This invention relates to an apparatus for operating a power transmission of a vehicle for use in a gear shift control apparatus of a manual transmission, to prevent misoperation.
A vehicle is provided with a power transmission for achieving smooth running under a complicated traveling condition. In general, this transmission controls the driving force and speed of the vehicle by changing engagement of a plurality of gears differing in the number of teeth or pitch. The transmission is to change the gear according to the traveling condition of the vehicle, and this type of transmission includes a manual transmission in which the driver manipulates a shift lever manually, and an automatic transmission in which a control apparatus automatically operates the transmission according to the traveling condition.
In the manual transmission, speed change is achieved by manipulating the shift lever provided in the vicinity of the driver's seat, and the shift lever includes a number of shift range patterns. In general, in a shift lever disposed on the floor of the vehicle, the shift lever is movable in the select direction which is right or left to the traveling direction of the vehicle, and also movable at each select position in the shift direction to the front and rear relative to the traveling direction of the vehicle.
On the other hand, in a transmission disposed adjacent to an engine, a control shaft which is movable in the axial direction and rotatable in the peripheral direction is provided on a housing. The housing is provided with a plurality of forward shift rails and reverse shift rails for linking the transmission gears, and a shift rag engaging with a shift finger is mounted to each shift rail. The shift lever and the control shaft are operably connected by a shift cable and a select cable.
To make a shift change of the transmission, when the driver operates the shift lever in the select direction to move the select cable, the control shaft of the transmission moves in the axial direction, and the shift finger engages with the shift rag of the selected position. When the shift lever is operated in the shift direction to move the shift cable, the control shaft of the transmission rotates to shift the shift rail through the shift rag engaging with the shift finger to link the gear to complete the shift change operation.
In such a manual transmission which has a plurality of forward shift ranges (1-5 speeds) and a reverse shift range (R: reverse), it is very dangerous to make a shift change to the reverse shift range in which the gear rotation is the reverse during operation of the shift lever in forward traveling of the vehicle. This may damage the gears. Therefore, the known manual transmission is provided with a misoperation prevention device.
The known misoperation prevention device can be operated with no resistance when making a shift change from the neutral position of the shift lever to a forward shift range (1-5 speed), but there is a moderate resistance when operating to the reverse shift range (R), making it difficult to make a shift change. Specifically, a block plate is mounted on the control shaft, and the housing is provided with an urged detent pin, so that when the shift lever is operated to the reverse range, the block plate contacts against the detent pin to produce a resistance. Therefore, when the shift lever is attempted to be shifted to the reverse range in the forward shift ranges (1-5 speeds), a resistance for the block plate to push in the detent pin is produced, thereby preventing misoperation of the shift lever during shift change operation.
In the misoperation prevention device in the above manual transmission, the detent pin to produce a resistance to the shift lever during shift change operation is urged by a coil spring. Since a quick shift change operation is required during running of the vehicle, operation of the shift lever is relatively rapid while the vehicle is running. Therefore, when the shift lever is attempted to be shifted to the reverse position by mistake during shifting in the forward 1st to 5th speeds, there has been a problem in that if the operation speed of the shift lever is high, the operation force is high, and the urging force of the coil spring does not make a resistance, resulting in a misoperation.
Then, to prevent such misoperation even when the operation speed of the shift lever is high, it is considered to set the urging force of the coil spring to a high value. However, this method involves a problem in that when the shift lever operation speed is low, that is, when the operation force is small, shift change to the reverse position is impeded to impair the shift change operability to the reverse position during ordinary operation.
With a view to solve the above mentioned problems, a primary object of the present invention is to provide an operation apparatus for a vehicle transmission which can positively prevent misoperation without impairing the shift change operability.